The present invention relates to traveling wave tube amplifiers (TWT Amplifiers) in general and in specific to a coupled cavity gyrotron-traveling-wave-tube amplifier for producing highly efficient, broad band millimeter wave radiation.
Many of today's high-tech military and commercial applications require a high power, broadband radiation source in the millimeter wave frequency range. Military applications for such TWT amplifiers include, but are not limited to, high resolution radar, communications and electronic jamming equipments. Commercial applications include, but are not limited to, equipment for high resolution airborne and ship-board navigation and communication systems, high efficiency satellite communications systems, millimeter-wave material processing, millimeter wave imaging systems and radiation source for laboratory test and measurement to name a few. Light weight, compact design and low cost are also critical factors for practical use and commercial production.
The use of free electron beams, linear and rotating, in vacuum tubes has been successful in producing multi-kilowatt high power, broadband radiation. Tens of kilowatts power in the millimeter wave frequency range with a large bandwidth, operating at a low beam voltage (&lt;60 kV ) is more attractive in today's TWT community.
Conventional approaches for achieving broadband rf amplification in the linear beam TWT-amplifiers are the use of a helix circuit supported by dielectric rods, an E-plane bend folded waveguide or the use of a staggered ladder circuits.
Millimeter wave helix circuits are generally too small to handle high peak and average power radiation. In both the ladder circuit and the folded waveguide, since the beam tunnel size is directly related to beam wave interaction impedance, the amount of beam power which can be injected into the circuit is limited by the small beam tunnel size. The radiation electronic efficiency of the linear beam devices in general is not more the 10%.
Until now approaches for attaining broadband rf amplification in the conventional gyro-TWT amplifiers have involved either loading disks, or dielectric material, into the waveguide to slow down the rf phase velocity of the wave, or tapering both the waveguide and the external magnetic field along the axial distance. In general, the gyro-devices are not suitable for high power, broadband millimeter wave radiation sources, due to the complexity of the circuit, the high magnetic field required, and the lengthy circuit.